Current pyrotechnic inflators for vehicle airbags contain filters to reduce the size of generant particles that are ejected from the inflator and to normalize the temperature of the exit gas.
Such filters can be made of spiral wraps of perforated steel plate. Because particulate builds up on such filters blocking the gas flow, a larger than practical flow area may be required or the perforation hole size may be bigger than desirable. A large portion of generant may be retained unburned in the depth of the filter reducing the inflator's efficiency and increasing its size.
Such compromise means that burning particles of generant ejected from the inflator as projectiles may cause direct damage to the airbag and may also elevate the temperature of the exit gases. It is often necessary to include expensive heat resistant cloth with the airbag or a separate metal heat shield or deflector with the inflator to protect the airbag from such damage.
It is therefore an objective to limit the absolute size of any solid particle ejected with generant gas to less than 20 micron spherical size, to improve burn efficiency of the inflator so that less generant is needed for a given performance, and to reduce performance variability. It is a further objective to be able to modify existing inflators and match their performance for the same or lower cost without requiring depth filtration.
These and other improvements over prior art inflators are achieved by the invention described hereinafter.